The first piece of armour that Paul tells you to put on in Ephesians 6:14 is the belt of truth: “Stand your ground, putting on the belt of truth and the body armor of God’s righteousness.” He first gives a command and tells you to stand your ground. This is important when going into battle. You must first stand your ground when in battle. Do not give up; do not shy away or the enemy will overtake you.
Then he says to put on the belt of truth. A belt holds everything together, just as the truth holds all of the armour together. The Christian life is based on truth. God is the God of truth who only speaks truth, while the devil stands on lies and speaks lies.
Paul then says to put on the body armour, the breast piece of righteousness that protects the most important organ, your heart. Your heart is what gives you life. If it stops, then you will no longer live. In the Christian life, your heart is what houses the Holy Spirit, the life of Christ. You must protect it from the enemy’s darts. Righteousness, living a holy life, is what protects you from the enemy. He cannot touch you when you are living according to the Lord and His truth.